The present invention relates to apparatus and method for navigating a mobile body such as a vehicle which achieve a road map display in a form of a bird's eye view on a display screen of a display unit.
A Japanese Patent Application First Publication No. Heisei 7-220055 published on Aug. 18, 1995 exemplifies a previously proposed navigating apparatus in which a topographical road map in the form of a bird's eye view (perspectively projected representation) is displayed on the screen of the display unit.
However, since the bird's eye view representation means that a region of the road map viewed obliquely from an upper sky as a viewpoint, a displayed road map is viewed in such a way that the road map is compressed in terms of its longitudinal direction. Hence, the following inconveniences are raised.
(1) A displayed angle of a road segment crossing at a traffic intersection with respect to a lateral axis on the displayed bird's eye view does not coincide with that of the road segment crossed at an actually corresponding intersection.
For example, the displayed angle of each road segment crossing the intersection in an example of the bird's eye view representation shown in FIG. 15 is different from that crossing the intersection in an example of a plan view (top view) representation (the same display as an actual road situation) shown in FIG. 16.
(2) Even if the display of the same road segment occurs in the same place, a length of the road segment is often varied according to a direction of a line of sight from the viewpoint of the bird's eye view.